In recent years, in order to detect a trouble portion and the like in a network, it is often required to recognize the connection relation (a network topology: hereafter, refer-red to as a topology) between terminals, switches and the like, which exist inside the network, in a network management. In an IP (Internet Protocol) router used in the Internet, typically, a network management function that can be used to determine the topology is installed in many cases. Thus, it is possible to easily determine the topology. On the other hand, in LAN (Local Area Network) such as IEEE802.3 (Ethernet (Registered Trademark)) and the like, low cost switches are used in many cases. In such switches, the management function for detecting the topology is not installed, which makes the determination of the topology difficult in many cases. As conventional techniques for detecting the topology in the LAN, there are following methods.
As a first conventional technique, a method for collecting connection information from switches and determining the topology in accordance with this information is generally known. The first conventional technique is described in, for example, Japanese Patent Application Publication JP-A-Heisei, 9-186716. In the technique described in Japanese Patent Application Publication JP-A-Heisei, 9-186716, each of the switches in the network collects addresses of the terminals connected to its own interface and other switches to determine the topology.
As a second conventional technique, there is a method in which the routers/switches which are passed by routes between terminals are investigated in turn to determine the topology. Conventionally, it is generally known that at the IP level, the topology can be estimated by a function which can detect routers which are passed in a route between, terminals in turn through the use of Traceroute and the like. On the other hand, even in the case of the Ethernet (Registered Trademark), similarly to the Traceroute, a function in which a response of a frame is obtained in the switch is standardized as IEEE802.1ag. Thus, the topology can be easily estimated by using the method similar to the Traceroute.
As a third conventional technique, there is a method in which a certain terminal transmits a packet to a plurality of different terminals and in each of the terminals receiving this packet, a correlative relation between qualities (throughputs, delays, packet losses and the like) obtained in the packet in the network is investigated, thereby determining the topology.
However, in the first and second conventional techniques, there is a problem in which, when network equipment which cannot use the management function used to detect the topology and the like exists in the network, the topology in that portion cannot be detected. In particular, the LAN is typically provided with low cost switches that do not have a management function. Such a low cost switch cannot use the management function and the IEEE802.1ag in many cases. Thus, in the LAN of the typical (low cost) configuration, it is difficult to detect the topology.
Further, in the third conventional technique, in order to determine the topology, it is required to install a topology detecting function at all of the terminals in the network. Thus, for establishing a network in which the topology can be detected, there is a problem that its cost becomes expensive.